Tort‐Colet, Núria

Abstract Background Sleep disturbances are common in Alzheimer's disease and have been reported in its preclinical stage. A detailed characterization of sleep disruption across the Alzheimer’s disease continuum is required to clarify its role as a potential therapeutic target and to evaluate the utility of sleep-related biomarkers. Methods Sleep architecture was characterized through detailed spectral and temporal analysis of the slow-wave activity using polysomnography across the Alzheimer’s disease continuum . Participants included: cognitively unimpaired individuals without abnormal Alzheimer’s disease biomarkers (n = 30), cognitively unimpaired individuals with abnormal Alzheimer’s disease biomarkers (n = 45), and individuals with mild cognitive impairment or mild dementia due to Alzheimer’s disease (n = 41). Associations between slow-wave features and longitudinal cognitive performance were tested in cognitively unimpaired participants. Sex differences were also explored. Results A stepwise increased wake after sleep onset and latency to rapid eye movement sleep was observed, alongside reduced spectral power of slow-wave activity and a progressive flattening of slow-waves across the Alzheimer’s disease continuum in both sexes. In cognitively unimpaired individuals, higher slow-wave slope and greater peak-to-peak amplitude were associated with better cognitive trajectories over time. Conclusions Sleep macro- and microarchitecture are altered early and progressively deteriorate across the Alzheimer’s disease continuum . Slow-wave features relate to cognitive trajectories in preclinical Alzheimer’s disease, with exploratory analyses suggesting stronger associations in men. These findings support slow-wave morphology as a candidate non-invasive marker for future sleep-based intervention studies.

Abstract INTRODUCTION Sleep disruption, particularly loss of slow‐wave sleep (SWS), is common in Alzheimer's disease (AD), but its neurobiological underpinnings remain unclear. We investigated whether locus coeruleus (LC) integrity relates to SWS across the AD continuum and whether sex and perivascular spaces (PVSs) modify these associations. METHODS In a cohort (11 controls, 30 mild cognitive impairment, 17 AD dementia) we combined overnight polysomnography with LC‐sensitive magnetic resonance imaging of the LC, basal ganglia and centrum semiovale PVS ratings, and cerebrospinal fluid noradrenaline. Multivariable linear regression adjusted for demographics, disease stage, and medication use. RESULTS Higher LC integrity was associated with greater slow‐wave activity and slow oscillation power, with stronger effects in females. Basal ganglia PVS burden was related to lower SWS spectral power, whereas noradrenaline levels were not associated with sleep. DISCUSSION LC integrity, sex, and PVS burden show associations with SWS alterations in aging and AD, supporting restorative sleep as a potential therapeutic target.